textproduct: Rapid City

KEY MESSAGES

- Dense fog through early this morning east of the Black Hills

- Mild and dry into next week.

UPDATE

Issued at 1155 PM MST Thu Nov 5 2026

Have hoisted a Dense Fog Advisory for portions of northwestern into south-central SD. Reports from SDHP and webcams indicate fog thickening and become more dense, which reflects expansion of stratus/fog per the nighttime microphysics satellite loop. Conditions favorable for additional expansion/development given upslope flow, clear skies, and T/Td spread convergence.

UPDATE Issued at 910 PM MST Thu Nov 5 2026

Upper ridge axis is centered across the Dakotas this evening. Surface obs show high pressure over eastern SD into northern MN, with return flow resulting in SE winds across western SD. Nighttime Microphysics Sat imagery shows clearly low clouds/fog across the eastern half of SD creeping into SCentral SD. Todd County webcams show dense fog over portions of the county. CAMs show fog expanding into the western SD plains through the night. The RRFS is farther west than the HRRR so have blended the two. Dense Fog Advisories may be needed later tonight. Clouds/fog will gradually erode and retreat eastward Fri morning into the early afternoon. Have cooled Max Ts across central SD to account for the delayed exit. No other changes needed with the forecast.

DISCUSSION

(This Afternoon Through Wednesday) Issued at 1102 AM MST Thu Nov 5 2026

Mean western NOAM ridging will support mild and dry weather as Pac flow continues aloft. Weak/skirting impulses will support cool fronts at times to knock temps down a few degrees. Temps will be above normal in the period with the warmest days being this weekend, particularity Sunday when highs will average 20 degrees above normal. The only expected impact in the period attm is for areas of fog toward central SD tonight. Moist BL with ESE upslope flow will support low clouds and fog later tonight there with fog and low clouds possibly shifting as far west as K2WX to KRAP. Any fog will quickly burn off Friday morning with temps recovering nicely by afternoon. Compact upper impulse will move through southern Canada on Friday and the the only impact from this system will be breezy winds across NW SD Sat. Another stronger trough will take a similar path across southern Canada on Sunday, supporting cool front into the area. This will knock temps back down into the 50s and 60s for Monday. Otherwise, no other impacts expected. This pattern looks to continue beyond the forecast period into the following weekend.

AVIATION

(For the 12Z TAFS Through 12Z Saturday Morning) Issued At 344 AM MST Fri Nov 6 2026

Expect IFR/LIFR conditions due to fog/stratus along/east of a line from K2WX-KPHP-KVTN through 06/15z. The KGCC/KRAP terminals should not be affected. Otherwise, VFR conditions are expected through the forecast period.

UNR WATCHES/WARNINGS/ADVISORIES

SD...Dense Fog Advisory until 9 AM MST /10 AM CST/ this morning for SDZ002-013-014-031-032-043-044-046-047-049-073-077-078. WY...None.